Nuvinci with a GXH50 on a USX

[cgbjake]

Damm you! Now I have a whole slew of things to think about. You bring up some very good points. I'll have to talk to Dave and see what he thinks. I think I'll still have room to do the major gear reduction on an added jack shaft and then run it to the Nuvinci. I really like the shifting hub idea, may have to reconsider everything though. Thanks a lot for chiming in, wish I didn't read it right before going to bed...it's 30 degrees out and I may end up in the garage tonight. This board is awesome!

Bret

 

[Alaskavan]

I think you'll find the 50cc will have more than enough power. The 35 would probably push a trike at 30 pretty easily, and would probly get better mileage.

Take lots of pics. Make it easy for us to copy you.

 

[duivendyk]

Sorry about possibly upsetting the applecart ,but look before you leap !,that hub is not cheap. You are pushing the envelope as far as application of the NV is concerned.I'm pretty sure David has been experimenting with this type of application.Call him on the phone (e-mail does not work),wether you'll get a straight story out of him is another matter.Good luck.

 

[duivendyk]

I recall that there are versions of the Honda engine with an add-on reduction drive (4?:1),used to drive pumps,that would be the ticket. You can get the final drive to compensate to get the overall ratio right.That would be a safe solution.It reverses the direction of rotation though,so you'd have to turn the engine around.

 

[Irish John]

I am trying to make sense of what you intend to do.you are driving the NV on the right side from your engine with an 11/60? chaindrive ,(60t sprocket same size as the hub??).This would be a freewheel.Then on the output of the NV mounted on the disk brake adapter you have a 14t output sprocket (can you mount anything that small there?, going to a 40t on the wheel.Assuming for the moment the NV to be 1:1,we have an overall ratio of
(60/11)x(40/14)=15.6.Roadspeed= .06 x rpm/R, R is the drive ratio.At 7000 rpm we get 0.06x7000/15.6=26.9 mph which is pretty close to your number (26.7).If you throw in the NV ratio
2-0.57 , from a reduction of 2 via 1 to 0.57 (1/1.75),we get a low speed of 13.45 mph and a top of 47 mph at 7k rpm.At 5k we get
9.6 and 33.6 mph.The NV hub will be running at far,far higher rpm than it's intended use as a bicycle hub, close to 1300 rpm it is designed for 200/300 rpm but at higher torque.There is a special friction fluid in there, Who knows how the thing behaves at 4-5 times normal rpm??.(centrifugal effects??).I advise you to contact David Staton,he has been playing around with these hubs as intermediate drives and may have useful info.Also are a 60t sprocket at the NV input & 14 t output practical?.

From what I've read on this site it seems to me that the NV hub doesn't really deliver any extra speed but enables you to go up hills without pedalling.
Considering that pedalling along with the bike is a pleasurable activity I see its benefits as being able to get up the really steep hills that are seldom encountered. There also seem to be cadence problems with pedalling which negate most of the benefits.
I presume the hub allows the motor to run at lower revs but I can't really be certain from the postings. If that is all the hub can do it doesn't seem to be that much of an advantage.
If the NV hub is geared to turn 3 times faster or slower than a normal hub I would have thought that the top speed would be about 65 mph but it's reported as being about 34 mph which is what the Honda will do on a 11T drive sprocket and a 48T rear sprocket. I can't fathom why it is such a dud.
Duivendyk, could you explain in laymans language why the NV is so disappointing?

 

[duivendyk]

The Nuvinci hub is no more a "dud" than a derailleur arrangement or a multi-geared rear hub is.It acts like a gear shift in a car, in low gear you can accellerate faster,in higher gear you can keep the engine from running too fast,or if you have a stiff headwind or a hill to climb you can get more needed torque to the drive wheel by multiplying the engine torque more (but running at lower speeds)
You seem to think that in order to attain higher speeds lower gearing (less reduction) is all that is required,you also need more engine power output.If you don't have that,you won't have either the torque and/or the speed.For example, at speeds above 25 mph the engine power requirements go up at close to the third power of speed,that means if you want to go from 25 mph to 30 mph,your engine power has to increase by (6/5)x (6/5)x(6/5)=1.72 that is by something like 70%..Let say it now takes 1.7 hp But to attain that you have to get the engine to deliver that power by running it at the speed at which it is capable of doing this,say at 7k rpm. The variable gearing will allow you to reduce that rpm to the rear axle rpm required to attain 30 mph.If you engine is not capable of that output your top speed will be less.The NV being a CVT is more flexible than a drive with fixed ratios. It also has a wide 3.5:1 ratio (0.5 to 1.75) and it can handle a fairly high input torque.It has a dual powerinput,one from the engine drive and a freewheel from the front crank.I happen to live in a very hilly area,the only flat areas are at the top and bottom of hills!,and a lot of these long hills are above 5% grades which are murder to get up with a bike even in super low gear.So for me the wide ratio is quite advantageous,but is an overkill in places with no or more moderate hills.A 3 speed hub like the SA ones (they make a newer version in Taiwan I recently learned) with ratios of 0.75-1-1.33 would be OK, the ratios are a bit wide but manageable.One disadvantage with any of these hubs is that you cadance is directly tied to the engine speed (the gearshift is BEHIND the combining input.So if your engine speed in normal use could vary by say over 50% so would your cadence,say from 60 to 90.not all that comfortable!.So I kept my front deraileur but ran into trouble with chain skipping due to poor design of the freewheel sprocket.I started a thread on that problem if you are interested.So far the NV seems to hold up pretty well.I'm not ecstatic about the handling of the bike with all that weight at the rear and never got quite used to it since I also ride a normal mountain bike.I hope you find this helpful.

 

[Irish John]

Thanks Duivendyk, that is helpfull. I don't think the front derailleur is ever going to work and how you manage to get it onto the wide crank is beyond me. I do like the sound of lower revs but I think the cadence would bother me. If I lived in an area with hills too steep to climb with the normal rig I would definitely consider one. I'm still waiting for a frame mounted version - Oh I see - you have a rear rig so you can have a front derailleur. Pity it can't handle the rear freewheel sprocket.
Until the frame mount is available I'll do without. Don Grube is working on a CVT hub and also on a belt drive - the latter is at prototype stage and the former is just an idea. Thanks for the info - it is very thorough.

 

[duivendyk]

The NV is not the only game intown only anymore when it comes to transmission options.The Staton gearbox+ NV hub are pretty solid but heavy with rather poor handling, which I happen to care about.There are these frame mount HT type engines kits with a drive to a jackshaft and then to a second sprocket on a freewheel crank to combine power inputs and then to a deraileur or a internally geared rear hub.You'd have a hard time getting started I think with the deraileur if you needed to pedal start (chain tension problems),so a internally geared hub would be needed.Should be lighter&cheaper and handle much better.Finding a reliable engine might be a bit of a problem.You can get the kit (minus engine) for about $200 I think.

 

[Irish John]

You're not talking about those 2 stroke shifter kits from sick bike parts are you? I don't even think about 2-strokes these days.

 

[duivendyk]

Yes I was,2 strokes aren't all bad,I rode a 2 stroke 350cc DKW once all the way from the Persian Gulf to the Hague.But this was a rugged,well engineered Teutonic machine.Had to take the heads off to clean things up in Croatia due to awful gas.My friends riding BSA's had a lot more trouble (unprotected chains &frame problems).The trouble is to find a Chinese one that last.Most require a rebuild right of the bat.(Bearings etc).But the inherent simplicity of a 2 stroke is hard to beat provided you build them right.My all time favorite was the RD 350,the best motorcycle ever in my opinion,great handling with adequate power.